Differential diagnosis of Lumbar spine symptoms

If I complain of L5/S1 bilateral symptoms provoked by extension and sideflexion of the lumbar spine with the arms at the side but when I have the arm elevated and repeat the same movements and I get no symptoms, better quality of movement- what can I hypothesise as having changed?

Have I improved stability by engaging the posterior sling?
Have i reduced the compression on the disc and stretch on the facet joint capsules hence reducing the pain?

How can i promote this movement in our daily lives? Should i stabilise the core or does manual therapy have a role in mobilising the dysfunction?
Or indeed both?

I am treating this client with a stabilty program, education(postural) and mobilising the Lsp PIVM l5/S1 in to rotation grade 3. Her comparable symptoms can also be reproduced with SLR and neck flexion and have started mobilisation of the neural system.

(Neuro tests all completed NAD)

Thank you for your thoughts.

hi, it sounds to me that you just change some biomechanics and thats why the symptoms change. but anyhow, core stability is always an important factor, as well as mobilisation. also make sure that hip has free/enough ROM, it might pull LS in wrong position and increase problems.
but your program sounds good to me. posture, exercises for abs and back, mobi etc. is all good. good luck
cheers